Nature Chemistry 6, 65–74 (2014); published online 8 December 2013; addendum published after print 21 March 2014.

After this Article went to press the authors realized that a number of the key references had been inadvertently omitted or removed before the final submission of the manuscript. The authors would therefore like to cite the following additional articles:

1. Zhu, M. L., Bendiak, B., Clowers, B. & Hill, H. H. Ion mobility-mass spectrometry analysis of isomeric carbohydrate precursor ions. Anal. Bioanal. Chem. 394, 1853–1867 (2009).

Structural characterization of select isomeric oligosaccharides using atmospheric ion-mobility spectrometry for separation of linkage and branch isomers, anomeric isomers, and epimers, prior to MS3 analysis using an ion-trap mass spectrometer.

2. Williams, J. P. et al. Characterization of simple isomeric oligosaccharides and the rapid separation of glycan mixtures by ion mobility mass spectrometry. Int. J. Mass Spectrom. 298, 119–127 (2010).

Using both travelling-wave ion-mobility spectrometry and drift-tube ion-mobility spectrometry, released N-glycans and isobaric glycans were separated for subsequent characterization by tandem MS. Theoretical modelling was also used to confirm experimentally determined collisional cross-section values.

3. Fenn, L. S. & McLean, J. A. Structural resolution of carbohydrate positional and structural isomers based on gas-phase ion mobility-mass spectrometry. Phys. Chem. Chem. Phys. 13, 2196–2205 (2011).

Details the collisional cross-section values of ∼300 sodiated positional and structural carbohydrate isomers from MALDI IM-MS.

4. Harvey, D. J. et al. Travelling wave ion mobility and negative ion fragmentation for the structural determination of N-linked glycans. Electrophoresis 34, 2368–2378 (2013).

Structural characterization of released N-glycans using negative-ion-mode collision-induced dissociation of ion-mobility-separated isomer (and conformer) precursors.